Corynebacterium glutamicum (ATCC 21253) was cultivated in a pH-auxostat. The flux partitioning at key branch nodes in the central metabolism train of C. glutamicum was used to illustrate the physiological responses subject to the influence of specific growth rates. In glycolysis, the flux partitioning at the G6P point (51.94 +/- 0.7%) was insensitive to variations of specific growth rate, whereas the partitioning decreased approximately 30% from PEP to PYR. In the TCA cycle, the specific growth rates had negligible effects on the flux partitioning at both OAA (76.80 +/- 1.19%) and FUM (70.46 +/- 2.42%) nodes, but had a significant effect on the AKG node (63.2, 43.26, and 30.65% corresponding to specific growth rates of 0.23, 0.45, and 0.51 h(-1), respectively). The flux partitioning at the anaplerotic pathway (from PEP to OAA) was maintained at 25.46 +/- 2.26% for all the specific growth rates tested. The flexibility of PYR and AKG nodes shows a potential gateway for altering amino acid distribution, whereas the rigidity of G6P. SUC, FUM and OAA nodes implies that enzymes that associate with these nodes are insensitive to the manipulation of specific growth rates. (C) 2002 Elsevier Science Ltd. All rights reserved.